Today 220 million Americans (80% of the US population) live in and around major cities (U.S. Census, 2000). Due to their high density of population and economic activities, US cities and their residents have become the primary object of terrorism schemes that aim to cause mass destruction and casualties (National Research Council, 2002).
Many biological and chemical warfare agents can be effectively spread to very large areas and affect many people through the air. These airborne harmful agents are particularly destructive in densely populated areas. such as shopping malls, subways, office buildings or stadiums. Due to their capacity to spread to large areas, airborne biological and chemical warfare agents are also the likely harmful agents that US troops will encounter in the battlefield abroad. In the War Against Terrorism, the development of sensitive devices to detect airborne harmful agents is critical for the protection of civilians in the US and our military personnel abroad.
Cell-based sensors provide sensitive and broadband detection of toxic agents without the specificity associated with traditional chemical sensors. Cell-based sensors can react to toxins similarly to “human” responses, providing an excellent first line screening device for harmful agents. The sensitivity and accuracy of cell-based sensors are primarily dependent on the physiology of the cells in the sensors. Cells with native (normal) physiology will provide better responses for sensors as their reactions to toxins resemble more closely the effects on a “whole” human, however, for direct gas sample testing, most types of cells cannot maintain normal physiology in the air-fluid interface (direct air contact) due to the fact that most cells function and live in the aqueous environment of the body.
Respiratory epithelial cells forming the lining of airway systems provide the first line of protection and responses for many inhaled harmful agents such as dust, air pollutants, chemicals and microbes as well as biological and chemical warfare agents. These airway epithelial cells reside in the interface of air and body fluid anc can maintain normal physiological functions in this unique environment. These unique properties of respiratory epithelial cells make them an ideal candidate for cell-based biosensors capable of detecting airborne harmful agents.